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SW180 little tweak of the collimation

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#1 Stopforths

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Posted 15 April 2019 - 01:34 PM

Just had a season on jupiter in what looked like good seeing but images weren't what i would expect of the sw180.

 

defocused a star and saw why collimation out a little bit.  I've added a focuser to the rear and was using a tak prism maybe this is why??

 

Anyway I used a simple system to id the  adjustment needed ( an object I could see over the front lined up with collimation screws.)

 

Then went to a star near the southern pole defocused and made a little adjustment which made it worse.  reversed this a couple of times checking and centering star each time and pretty much found perfection.  i was using 233 x a 12.5mm ortho.

 

Then went to jupiter and oh boy what an improvement ovals festoons grs coming round  amazing detail.  its virtually overhead here at 0500 in the morning.

 

I left scope out to acclimatize overnight. 

 

Collimation is so important and relatively easy with a sw mak.


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#2 Cali

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Posted 15 April 2019 - 01:37 PM

What focuser did you add?

 

- Cal



#3 macdonjh

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Posted 15 April 2019 - 01:52 PM

 

Collimation is so important and relatively easy with a sw mak.

Agreed, collimation is likely the most important variable that an observer can control in determining how good an image his scope will produce.  Seeing might be more important, but who can control seeing?



#4 Stopforths

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Posted 16 April 2019 - 11:22 AM

a gso crayford 10/1

 

works great.  there is a little mirror shift in the sw180 and the sw focuser isn't precise enough for my liking also its a bit stiff.

 

I also have a IM10 inch mak cass and the focuser on that is next to useless even after a reassembly.  I use a gso on that also and it works great.

 

Its a slow difficult process using that scope without the gso and I'm glad I have one.  Shame because optics are superb in the big Mak.

 

Just got in after a season on jupiter in the 10  seeing came and went but at 280 x there was plenty to see.

 

 

 

What focuser did you add?

 

- Cal



#5 Bill Barlow

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Posted 17 April 2019 - 09:26 AM

When you adjusted the collimation on your 180 MAK, did you loosen the one large mirror lock screw and adjust the smaller collimation screw where the adjustment was needed?  Or did you loosen all three large primary mirror locking screws and then adjust the smaller one?  Also, what is the diameter of the rear cell opening in these scopes?  Thanks.

 

Bill



#6 Peter Besenbruch

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Posted 17 April 2019 - 09:48 PM

When I collimated my 180, I loosened the three small screws, collimated with the three big screws, and very gradually tightened the three little screws. Of course, it helps if the scope is pointing up, you use very high powers, and you keep re-centering the star. Also, it's a good idea to collimate straight through if you are at all uncertain about your diagonal's alignment.



#7 luxo II

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Posted Yesterday, 06:06 AM

Collimation is important - PERIOD.

Many users think “near enough is good enough” without realising that the difference between nailing it spot on vs “a bit off” is cheese vs chalk.

Laser collimation gadgets will get it close but not perfect - there is no substitute for collimating on a real star.

And this applies to all cassegrains, maks and SCTs - as well as newtonians and refractors.

For a SW mak, follow Peters advice above. The target star should be 70 degrees elevation or higher.

Edited by luxo II, Yesterday, 06:17 AM.


#8 Bill Barlow

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Posted Yesterday, 09:13 AM

When I collimated my 180, I loosened the three small screws, collimated with the three big screws, and very gradually tightened the three little screws. Of course, it helps if the scope is pointing up, you use very high powers, and you keep re-centering the star. Also, it's a good idea to collimate straight through if you are at all uncertain about your diagonal's alignment.

Someone on another thread that owns a SW 180 MAK said he collimated using the three smaller screws and tightens down the primary mirror with the large ones.  I guess you can collimated both ways then?

 

Bill



#9 fcathell

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Posted Yesterday, 02:27 PM

Peter B. made a good point about having the scope pointing up rather than being horizontal as it probably would be with an artificial star. Due to the mirror's downward weight, I can see how loosening all of the similar collimation screws would be advantageous.  With a horizontally mounted scope this would not be recommended due to the mirror's weight pushing laterally.  In this case tiny incremental adjustments must be made with subsequent snugging of individual screw sets each time.

 

Frank



#10 Peter Besenbruch

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Posted Yesterday, 02:43 PM

Someone on another thread that owns a SW 180 MAK said he collimated using the three smaller screws and tightens down the primary mirror with the large ones.  I guess you can collimated both ways then?

My understanding is that the little screws function as lock screws and the big screws do the actual pushing around. What I like about the 180 is that they are paired.



#11 Peter Besenbruch

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Posted Yesterday, 02:44 PM

Peter B. made a good point about having the scope pointing up rather than being horizontal as it probably would be with an artificial star. Due to the mirror's downward weight, I can see how loosening all of the similar collimation screws would be advantageous.  With a horizontally mounted scope this would not be recommended due to the mirror's weight pushing laterally.  In this case tiny incremental adjustments must be made with subsequent snugging of individual screw sets each time.

Agreed.



#12 James Ball

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Posted Yesterday, 06:32 PM

I have the SW150 and need to check the collimation, just wondering if 180x is enough magnification or if I need to pick up a higher magnification eyepiece.  Right now I only have a 25mm Meade that came with the ETX90 and the 10mm VixenLV.




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